将包含where，group by，sum和得Linq的MySQL语句转换为Sql

Question

我正在尝试将以下MySql转换为Linq转换为Sql（有或没有Lambda体验）

从table.column2 <'2014-11-27 00:00:00'的表中选择*，按具有sum（table.column3 = 0）> sum（table.column3 = 1）的table.column1分组

有可能吗？如果有的话吗？

Column1是字符串，Column2是DateTime，Column3是TinyInt（布尔）

Answer 1

IQueryable<MyType> query = // get table IQueryable from the Linq2Sql data context

var dateTime = DateTime.Parse("2014-11-27");
var result = query.Where(t => t.Column2 < dateTime)
    .GroupBy(t => t.Column1)
    // Linq doesn't have HAVING, you can just use Where(). Here, we're operating on
    // an IQueryable of IGrouping, and we're filtering based on taking sums over the groups
    .Where(g => g.Sum(t => !t.Column3 ? 1 : 0) > g.Sum(t => t.Column3 ? 1 : 0))
    // it's not clear to me what you want here. Without any Select, each full grouping will get
    // pulled into memory as an IGrouping. If instead you just want the Column1 values, you'd
    // want .Select(g => g.Key)
    .Select(...);

注意，我在这里假设您已将Column3映射到实体类中的bool。 如果改为将其作为字节，则必须执行t.Column3 == 0而不是!t.Column3 。